Recently, as the depletion of an energy resource such as petroleum or coal is expected, the interest in the substitute energy has been more increased. In this regard, a solar cell converting solar energy into electrical energy has been spotlighted.
A solar cell (or photovoltaic cell) is a core element in solar power generation to directly convert solar light into electricity.
For example, if the solar light having energy greater than band-gap energy of a semiconductor is incident into a solar cell having the PN junction structure of a semiconductor, electron-hole pairs are generated. As electrons and holes are collected into an N layer and a P layer, respectively, due to the electric field formed in a PN junction part, photovoltage is generated between the N and P layers. In this case, if a load is connected to electrodes provided at both ends of the solar cell, current flows through the solar cell.
The current generated from the solar cell is transferred to a junction box through a bus bar. In general, the bus bar is formed on the front surface of a solar cell panel and extends to a rear surface of the solar cell panel through a hole formed in the solar cell panel to allow the current to flow into the junction box.
In this case, the bus bar may be provided on a top surface of the back electrode layer in the solar cell. In this case, the surface of the back electrode layer may have mutually different compositions according to the parts of the solar cell. The degree of charge collection may be variable depending on positions of bus bars due to the state variation on the surface of the back electrode layer.
Accordingly, there is required a solar cell having a novel structure capable of improving charge collection when the bus bar is formed on the solar cell panel.